With the bishop pair and a powerful pawn center, there's no doubt about White's advantage, but perhaps it's not as big as it seems. In any case, Fedoseev is an almost unparalleled master at turning questionable positions into victories.
13... b7b6 This move has never been played before, according to my database. Black wants to continue the thematic development of the bishop on a6. 14. e3e4  14... c8a6  15. c3c4 It's important to avoid the exchange since the pair of bishops is precisely one of the reasons for White's advantage. 15... a5d2 